Final answer:
Oblique modes refer to wave motion that is not perpendicular to the boundary between two mediums, while tangential modes have wave motion that is parallel to the boundary.
Step-by-step explanation:
In physics, oblique and tangential modes refer to the different types of motion in wave propagation. In the case of oblique modes, the wave motion is not perpendicular to the boundary between two mediums. On the other hand, tangential modes have wave motion that is parallel to the boundary.
For example, consider a wave traveling from one medium to another at an angle. In oblique modes, the wave will change direction and undergo both reflection and refraction. In tangential modes, the wave will continue to propagate in the same direction parallel to the boundary.
Understanding the difference between these modes is important in practical applications such as waveguides, fiber optics, and acoustics.